1. Field of the Invention
The present invention relates to a cell-size inspection device which is preferable for use in the inspection of the cell size of the supporting grid supporting the nuclear fuel rod provided in the nuclear fuel assembly.
2. Prior Art
In the nuclear fuel assembly, plural plate-shaped straps are assembled perpendicularly to each other into the grid shape, so that the supporting grids each providing plural cells into which nuclear fuel rods are inserted will be formed. When the nuclear fuel rod is inserted into each of the cells of the supporting grid, springs provided in each cell elastically presses the nuclear fuel rod against the walls of the cells, so that the nuclear fuel rods are supported by the supporting grid.
In the above-mentioned assembling method of the nuclear fuel assembly, when inserting the fuel rod into each cell, the springs provided in each cell must come in contact with the fuel rod. This occurs a possibility in that flaws may be formed on the surface of the fuel rod.
In order to cope with such difficulty, the prior-art assembling method is proposed such that prior to the insertion of the fuel rod, a key member is inserted into the supporting grid so as to broaden the springs of each cell.
In the above-mentioned method, in order to ascertain the safe insertion of the fuel rod, prior to the insertion of the fuel rod, a pin gauge having the predetermined size is inserted into each of the cells so as to inspect the inside size of each cell. In this case, by judging the insertion manner of the pin gauge by human eyes, the inspection is performed on the inside size of the cell of which springs are broadened.
However, in the above-mentioned inspection method, a plenty of cells must be inspected one by one by the human. For this reason, when inspecting all of the cells, it takes many working hours and inspectors, which raises a drawback in that the inspection cannot be made efficiently. In addition, since the cell size is inspected visually, there exist differences among individuals, which raises another drawback in that the standardization of the inspection operations among the inspectors must be difficult.